Superabsorbent crosslinked ampholytic ion pair copolymers

Abstract

The present invention provides crosslinked ampholytic ion pair (2-methacryloyloxyethyldiethylammonium cation (MEDEA)/sulfonate anion) copolymers that are highly absorbent to aqueous electrolyte solutions. The polymers of the present invention comprise polymers formed by the copolymerization of an effective amount of each of the following components to produce a polymer which is highly absorbent to aqueous electrolyte solutions: (a) an ampholytic ion pair monomer comprising (i) the ammonium cation 2-methacryloyloxyethyldiethylammonium and (ii) a sulfonate anion selected from the group consisting of 2-acrylamido-2-methylpropane sulfonate, 2-methacryloyloxyethane sulfonate, vinyl sulfonate, styrene sulfonate and combinations of two or more thereof; (b) at least one comonomer selected from the group consisting of acrylamide, methacrylamide, acylonitrile, acrylic acid, methacrylic acid, alkali salts of acrylic acid, alkali salts of methacrylic acid, 2-methacryloyloxyethyldiethylamine, 2-acrylamido-2-methylpropane sulfonic acid, alkali salts of 2-acrylamido-2-methylpropane sulfonic acid, 2-methacryloyloxyethane sulfonic acid, alkali salts of 2-methacryloyloxyethane sulfonic acid, N-vinyl-2-pyrrolidone and combinations of two or more thereof; and (c) at least one crosslinking agent which has at least two polymerizable olefinic functionalities wherein the olefinic functionalities are suitable for crosslinking. The invention also provides a method of using the polymers of the present invention for absorbing an aqueous electrolyte solution comprising the step of contacting the polymers of the present invention with an aqueous electrolyte solution.

We claim: 
     
       1. A polymer formed by the copolymerization of an effective amount of each of the following components to produce a polymer which will absorb at least 70 grams of synthetic urine per gram of polymer: (a) an ampholytic ion pair monomer comprising (i) the ammonium cation 2-methacryloyloxyethyldiethylammonium and   (ii) a sulfonate anion selected from the group consisting of 2-acrylamido-2-methylpropane sulfonate, 2-methacryloyloxyethane sulfonate, vinyl sulfonate, styrene sulfonate, and combinations of two or more thereof;     (b) at least one comonomer selected from the group consisting of acrylamide, methacrylamide, acrylonitrile, acrylic acid, methacrylic acid, alkali salts of acrylic acid, alkali salts of methacrylic acid, N-vinyl-2-pyrrolidone and combinations or two or more thereof; and   (c) at least one crosslinking agent which has at least two polymerizable olefinic functionalities wherein each of the olefinic functionalities is suitable for crosslinking.   
     
     
       2. The polymer of claim 1 wherein the crosslinking agent is selected from the group consisting of N,N-diallylmethacrylamide, diallylamine, N,N-bisacrylamidoacetic acid, N,N'-bisacrylamidoacetic acid methylester, N,N'-methylenebisacrylamide (methylene-bis-acrylamide), N,N-benzylidenebisacrylamide, allylacrylate, diisopropenylbenzene, diallyl succinate, ethylene glycol diacrylate, diallylacrylamide, divinylbenzene, and combinations of two or more thereof. 
     
     
       3. The polymer of claim 2 wherein the crosslinking agent comprises N,N'-methylenebisacrylamide. 
     
     
       4. The polymer of claim 1 wherein the polymer is at least partially hydrolyzed. 
     
     
       5. The polymer of claim 1 wherein the polymer is at least partially neutralized. 
     
     
       6. The polymer of claim 1 wherein the comonomer is selected from the group consisting of acrylamide, acrylonitrile, acrylic acid, alkali salts of acrylic acid, and combinations of two or more thereof. 
     
     
       7. The polymer of claim 6 wherein the comonomer is acrylamide. 
     
     
       8. A polymer formed by the copolymerization of an effective amount of each of the following components to produce a polymer which is highly absorbent to aqueous electrolyte solutions: (a) an ampholytic ion pair monomer comprising (i) the ammonium cation 2-methacryloyloxyethyldiethylammonium and   (ii) a sulfonate anion selected from the group consisting of 2-acrylamido-2-methylpropane sulfonate, 2-methacryloyloxyethane sulfonate, vinyl sulfonate, styrene sulfonate, and combinations of two or more thereof;     (b) a comonomer selected from the group consisting of acrylamide and methacrylamide;   (c) at least one crosslinking agent which has at least two polymerizable olefinic functionalities wherein each of the olefinic functionalities is suitable for crosslinking;   wherein the polymer is formed by the polymerization of in the range of about 3 mole percent to about 50 mole percent of the ampholytic ion pair monomer, and in the range of about 50 mole percent to about 97 mole percent of the comonomer wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and in the range of of about 0.01 mole of the crosslinking agent to about 0.3 mole of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       9. The polymer of claim 8 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 30 mole percent of the ampholytic ion pair monomer, and   (b) in the range of about 70 mole percent to about 97 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.03 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       10. The polymer of claim 8 wherein the sulfonate anion is 2-acrylamido-2-methylpropane sulfonate. 
     
     
       11. The polymer of claim 10 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 30 mole percent of the ampholytic ion pair monomer, and   (b) in the range of about 70 mole percent to about 97 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       12. The polymer of claim 11 wherein the polymer is formed by the polymerization of: (a) in the range of about 5 mole percent to about 20 mole percent of the ampholytic ion pair monomer, and   (b) in the range of about 80 mole percent to about 95 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.03 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       13. The polymer of claim 8 wherein the sulfonate anion is 2-methacryloyloxyethane sulfonate. 
     
     
       14. The polymer of claim 13 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 50 mole percent of the ampholytic ion pair monomer, and   (b) in the range of about 50 mole percent to about 97 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       15. The polymer of claim 14 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 30 mole percent of the ampholytic ion pair monomer, and   (b) in the range of about 70 mole percent to about 97 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.02 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       16. The polymer of claim 6 wherein the comonomer is acrylonitrile. 
     
     
       17. A polymer formed by the copolymerization of an effective amount of each of the following components to produce a polymer which is highly absorbent to aqueous electrolyte solutions; (a) an ampholytic ion pair monomer comprising (i) the ammonium cation 2-methacryloyloxyethyldiethylammonium and   (ii) a sulfonate anion selected from the group consisting of 2-acrylamido-2-methylpropane sulfonate, 2-methacryloyloxyethane sulfonate, vinyl sulfonate, styrene sulfonate, and combinations or two or more thereof;     (b) an acrylonitrile comonomer and;   (c) at least one crosslinking agent which has at least two polymerizable olefinic functionalities wherein each of the olefinic functionalities is suitable for crosslinking;   wherein the polymer is formed by the polymerization of in the range of 3 mole percent to about 30 mole percent of the ampholytic ion pair monomer, and in the range of about 70 mole percent to about 97 mole percent of the acrylonitrile comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and in the range of about 0.01 mole of the crosslinking agent to about 0.3 mole of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       18. The polymer of claim 17 wherein the polymer is formed by the polymerization of: (a) in the range of about 5 mole percent to about 25 mole percent of the ampholytic ion pair monomer, and   (b) in the range of about 75 mole percent to about 95 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.03 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       19. The polymer of claim 17 wherein the sulfonate anion is 2-acrylamido-2-methylpropane sulfonate. 
     
     
       20. The polymer of claim 19 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 25 mole percent of the ampholytic ion pair monomer, and   (b) in the range of about 75 mole percent to about 97 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       21. The polymer of claim 20 wherein the polymer is formed by the polymerization of: (a) in the range of about 5 mole percent to about 20 mole percent of the ampholytic ion pair monomer, and   (b) in the range of about 80 mole percent to about 95 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.03 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       22. The polymer of claim 17 wherein the sulfonate anion is 2-methacryloyloxyethane sulfonate. 
     
     
       23. The polymer of claim 22 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 30 mole percent of the ampholytic ion pair monomer, and   (b) in the range of about 70 mole percent to about 97 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       24. The polymer of claim 23 wherein the polymer is formed by the polymerization of: (a) in the range of about 6 mole percent to about 25 mole percent of the ampholytic ion pair monomer, and   (b) in the range of about 75 mole percent to about 94 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.03 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       25. The polymer of claim 6 wherein the comonomer is a alkali salt of acrylic acid. 
     
     
       26. A polymer formed by the copolymerization of an effective amount of each of the following components to produce a polymer which is highly absorbent to aqueous electrolyte solutions: (a) an ampholytic ion pair monomer comprising (i) the ammonium cation 2-methacryloyloxyethyldiethylammonium and   (ii) a sulfonate anion selected from the group consisting of 2-acrylamido-2-methylpropane sulfonate, 2-methacryloyloxyethane sulfonate, vinyl sulfonate, styrene sulfonate, and combinations of two or more thereof;     (b) a comonomer selected from the group consisting of acrylic acid, methacrylic acid, alkali salt of acrylic acid and alkali salts of methacrylic acid and;   (c) at least one crosslinking agent which has at least two polymerizable olefinic functionalities wherein each of the olefinic functionalities is suitable for crosslinking;   wherein the polymer is formed by the polymerization of in the range of about 3 mole percent to about 6 mole percent of the ampholytic ion pair monomer, and in the range of about 94 mole percent to about 97 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 percent; and in the range of about 0.01 mole of the crosslinking agent to about 0.3 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       27. The polymer of claim 26 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 6 mole percent of the ampholytic ion pair monomer, and   (b) in the range of about 94 mole percent to about 97 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       28. The polymer of claim 26 wherein the sulfonate anion is 2-acrylamido-2-methylpropane sulfonate. 
     
     
       29. The polymer of claim 28 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 6 mole percent of the ampholytic ion pair monomer, and   (b) in the range of about 94 mole percent to about 97 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       30. The polymer of claim 29 wherein the polymer is formed by the polymerization of: (a) about 3 mole percent of the ampholytic ion pair monomer, and   (b) about 97 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.03 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       31. The polymer of claim 26 wherein the sulfonate anion is 2-methacryloyloxyethane sulfonate. 
     
     
       32. The polymer of claim 31 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 6 mole precent of the ampholytic ion pair monomer, and   (b) in the range of about 94 mole percent to about 97 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       33. The polymer of claim 32 wherein the polymer is formed by the polymerization of: (a) about 3 mole percent of the ampholytic ion pair monomer, and   (b) about 97 mole percent of the comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.03 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       34. The polymer of claim 6 wherein the comonomer is a combination of acrylamide and alkali salt of acrylic acid. 
     
     
       35. A polymer formed by the copolymerization of an effective amount of each of the following components to produce a polymer which is highly absorbent to aqueous electrolyte solutions: (a) an ampholytic ion pair comprising (i) the ammonium cation 2-methacryloyloxyethydiethylammonium and   ii) a sulfonate anion selected from the group consisting of 2-acrylamido-2-methylpropane sulfonate, 2-methacryloyloxyethane sulfonate, vinyl sulfonate, styrene sulfonate, and combinations of two or more thereof;     (b) a comonomer which is a combination of acrylamide and an alkali salt of acrylic acid and;   (c) at least one crosslinking agent which has at least two polymerizable olefinic functionalities wherein each of the olefinic functionalities is suitable for crosslinking;   wherein the polymer is formed by the polymerization of in the range of about 1 mole percent to about 55 mole percent of the ampholytic ion pair monomer, in the range of about 10 mole percent to about 55 mole percent of the acrylamide comonomer, and in the range of about 32 mole percent to about 89 mole percent of the alkali salt of acrylic acid comonomer, wherein the total amount of the ampholytic ion pair monomer and comonomer equals 100 mole percent; and in the range of about 0.01 mole of the crosslinking agent to about 0.3 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       36. The polymer of claim 35 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 50 mole percent of the ampholytic ion pair monomer,   (b) in the range of about 13 mole percent to about 50 mole percent of the acrylamide comonomer, and   (c) in the range of about 37 mole percent to about 84 mole percent of the alkali salt of acrylic acid comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (d) in the range of about 0.03 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       37. The polymer of claim 35 wherein the sulfonate anion is 2-acrylamido-2-methylpropane sulfonate. 
     
     
       38. The polymer of claim 37 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 15 mole percent of the ampholytic ion pair monomer,   (b) in the range of about 15 mole percent to about 30 mole percent of the acrylamide comonomer, and   (c) in the range of about 55 mole percent to about 82 mole percent of the alkali salt of acrylic acid comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (d) in the range of about 0.01 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       39. The polymer of claim 38 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 10 mole percent of the ampholytic ion pair monomer,   (b) in the range of about 20 mole percent to about 25 mole percent of the acrylamide comonomer, and   (c) in the range of about 70 mole percent to about 77 mole percent of the alkali salt of acrylic acid comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (d) in the range of about 0.03 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       40. The polymer of claim 35 wherein the sulfonate anion is 2-methacryloyloxyethane sulfonate. 
     
     
       41. The polymer of claim 40 wherein the polymer is formed by the polymerization of: (a) in the range of about 1 mole percent to about 55 mole percent of the ampholytic ion pair monomer,   (b) in the range of about 10 mole percent to about 55 mole percent of the acrylamide comonomer, and   (c) in the range of about 32 mole percent to about 89 mole percent of the alkali salt of acrylic acid comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (d) in the range of about 0.01 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       42. The polymer of claim 41 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 50 mole percent of the ampholytic ion pair monomer,   (b) in the range of about 13 mole percent to about 50 mole percent of the acrylamide comonomer, and   (c) in the range of about 37 mole percent to about 84 mole percent of the alkali salt of acrylic acid comonomer,   wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (d) in the range of about 0.03 mole of the crosslinking agent to about 0.2 mole of the crosslinking agent per 100 mole of the ampholytic ion pair monomer and the comonomer.   
     
     
       43. A paper towel containing therein a polymer formed by the copolymerization of an effective amount of each of the following components to produce a polymer which will absorb at least 70 grams of synthetic urine per gram of polymer: (a) an ampholytic ion pair monomer comprising (i) the ammonium cation 2-methacryloyloxyethyldiethylammonium and   (ii) a sulfonate anion selected from the group consisting of 2-acrylamido-2-methylpropane sulfonate, 2-methacryloyloxyethane sulfonate, vinyl sulfonate, styrene sulfonate, and combinations of two or more thereof;     (b) at least one comonomer selected from the group consisting of acrylamide, methacrylamide, acrylonitrile, acrylic acid, methacrylic acid, alkali salts of acrylic acid, alkali salts of methacrylic acid, N-vinyl-2-pyrrolidone and combinations of two or more thereof; and   (c) at least one crosslinking agent which has at least two polymerizable olefinic functionalities wherein each of the olefinic functionalities is suitable for crosslinking.   
     
     
       44. A disposable diaper containing therein a polymer formed by the copolymerization of an effective amount of each of the following components to produce polymer which will absorb at least 70 grams of synthetic urine per gram of polymer: (a) an ampholytic ion pair monomer comprising (i) the ammonium cation 2-methacryloyloxyethyldiethylammonium and   (ii) a sulfonate anion selected from the group consisting of 2-acrylamido-2-methylpropane sulfonate, 2-methacryloyloxyethane sulfonate, vinyl sulfonate, styrene sulfonate and combinations of two or more thereof;     (b) at least one comonomer selected from the group consisting of acrylamide, methacrylamide, acrylonitrile, acrylic acid methacrylic acid, alkali salts of acrylic acid, alkali salts of methacrylic acid, N-vinyl-2-pyrrolidone and combinations of two or more thereof; and   (c) at least one crosslinking agent which has at least two polymerizable olefinic functionalities wherein each of the olefinic functionalities is suitable for crosslinking.